Laminated magnetic core structures for transformers or choke coils of great power



3,428,930 STRUCTURES FOR TRANSFOR MERS Feb. 18, 1969- A. H. TH. J.SLIEPENBEEK' LAMINATED MAGNETIC CORE OR CHOKE COILS OF GREAT POWER FiledJan. 16, 1968 INVENT'OR Amomus H. T. J. SLFEPENBEEK 9009-162.

B y k ATTORNEYS United States Patent ()ffice 3,428,930 Patented Feb. 18,1969 6701226 US. Cl. 336-212 2 Claims Int. Cl. H01f 27/24 ABSTRACT OFTHE DISCLOSURE A laminated magnetic core has three leg members extendingwith their central longitudinal axes in the longi; tudinal edges of anequilateral prism, two star-shaped yoke members, each of which consistsof three abutting yoke arms enclosing angles of 120, and couplingmembers, each of which connects an end of a leg member with the free endof a yoke arm. Each yoke arm has a central longitudinal axis whichintersects, at a common point, the longitudinal axes of the remainingtwo yoke arms of a yoke member. In at least a part of the total numberof layers of laminations of the yoke members, each yoke arm abuts thetwo other yoke arms with two straight end edges enclosing an angle of120. The projections of said end edges on a line extending in thedirection of the width of the yoke arm have unequal lengths. In the saidlayers each yoke arm consists of two laminations extending sideby-sideand abutting each other with longitudinal edges which are parallel tothe central longitudinal axis of the relevant yoke arm. Each one of saidlaminations is bounded at its end facing another yoke arm by a straightedge only, so that said laminations have widths which are equal to thesaid projections of said end edges, and the abutting longitudinal edgesof the said two laminations of each yoke arm are in offset relation toeach other in the direction of said longitudinal edges.

The invention relates to a laminated magnetic core structure for atransformer or a choke coil of great power, comprising three leg membersextending with their central longitudinal axes in the longitudinal edgesof an equilateral prism, two star-shaped yoke members, each of whichconsists of three abutting yoke arms enclosing angles of 120 and havingcentral longitudinal axes, which intersect in a common point, andcoupling members, each of which connects an end of a leg member with thefree end of a yoke arm, and in which core structure in at least a partof the total number of layers of laminations of the yoke members eachyoke arm abuts the two other yoke arms with two straight end edgesenclosing an angle of 120, the projections of said end edges on a lineextending in the direction of the width of the yoke arm having unequallengths.

A magnetic core structure of this kind is disclosed in the US. patentspecification 3,195,090 (FIGS. 4, 5a, b, c). In this known corestructure each yoke arm consists in each of the said layers of a singlelamination, of which the width is equal to that of the relevant yoke armand the end edges abutting the laminations of the two other yoke armsmeet in a salient angular point of 120. The yoke arms cannot be madebroader than the broadest available laminations. The cutting of thelaminations in the required shape causes a considerable loss ofmaterial, since the laminations cannot be fitted together to form anuninterrupted area due to their salient angular points of 120.

The invention has the object to provide a similar magnetic corestructure, which has some advantages over the known core structure owingto its special construction of the yoke members. It is characterized inthat in the said layers each yoke arm consists of two laminationsextending side by side and abutting each other with longitudinal edgeswhich are parallel to the central longitudinal axis of the relevant yokearm, each one of said laminations being bounded at its end facinganother yoke arm by a straight'end edge only, so that said laminationshave widths which are equal to the said projections of said end edges,and the angular points defined by said end edges and the abuttinglongitudinal edges of the said two laminations of each yoke arm lying inoffset relation to each other in the direction of said longitudinaledges. Since in this construction of the magnetic core structure eachyoke arm may consist in each layer of two laminations extending side byside in respect of its longitudinal axis, said yoke arms may be madebroader than the broadest laminations available. Owing to the dilferentwidths and to the offset relation of the angular points at the ends ofthe individual sets of laminations facing the common point ofintersection, the longitudinal joints between the adjacent laminationsin each one of the yoke arms and the joints between the end edges of theabutting laminations of different yoke arms are overlapped in afavourable manner, if layers or groups of layers having a givenarrangement of the laminations alternate with layers or groups of layershaving the symmetrical arrangement of the laminations. Moreover, theyoke members can be stacked of laminations which have only two differentshapes. Furthermore it is easily possible to obtain between the freeends of the yoke arms and the coupling members of the core structure aconnection, in which the joints between the yoke arms and the couplingmembers are favourably overlapped. An important advantage is also thatthe laminations can be cut from strips of appropriate widths without anyloss of material.

The structure constructed in accordance with the invention permits to sorotate the two end edges directed at an angle of to one another andbounding the end of a layer of a yoke arm facing the common point ofintersection in respect of the longitudinal direction of said yoke armas to make them equally long. This has the advantage that thelaminations of different yoke arms abutting each other with their endedges are in contact with one another for the longest possible lengthand the magnetic flux is led from one lamination into the other in themost favourable way. Cavities in the magnetic core structure due tounequal lengths of said abutting end edges are then avoided.

The invention will be further elucidated with the aid of the drawing. Inthe drawing is:

FIG. 1 in perspective a laminated magnetic core structure according tothe invention,

FIG. 2 on a larger scale a plan view of a layer of laminations of a yokemember for a magnetic core struc ture shown in FIG. 1, and

FIG. 3 on a larger scale a plan view of a layer of laminations of avariant of the yoke member shown in FIG. 2.

In FIG. 1 of the drawing three vertical leg members extending with theircentral longitudinal axes in the longitudinal edges of an equilateralprism are designated by 1, three horizontal yoke arms, of which thelongit-udinal axes intersect in a common point 3 of intersection andenclose angles of 120 are indicated by 2 and circlecylindrically curvedcoupling members extending between said leg members and said yokemembers are designated by 4, said leg, yoke and coupling membersconstituting the magnetic core structure of a transformer or a chokecoil of-large power.

In each layer the leg members and the coupling members consist of twolaminations of equal widths separated by a cooling gap 5 from oneanother. From FIG. 2 it appears that the yoke members consist in eachlayer of two different laminations 6, 7 per yoke arm 2 and that saidlaminations have unequal widths and are each bounded by a straight endedge 8, 9 at their ends facing the other yoke arms. Each lamination 6 ofa yoke arm abuts with its end edge 8 the end edge 9 of a lamination 7 ofanother yoke arm 2 and vice versa. The laminations 6 and 7 of each yokearm abut each other with longitudinal edges 10, 11 parallel to thelongitudinal axis of said yoke arm and their end edges 8 and 9 aredirected at an angle of 120 to one another and define together with saidlongitudinal edges 10, 11 angular points of 60, which lie in offsetrelation in the direction of the longitudinal axis. It will be apparentthat in the core structure layers, in which the laminations of each yokearm are arranged in a given way, alternate with layers, in which saidlaminations are arranged in the symmetrical way. Such a symmetricallyarranged layer is indicated in FIG. 2 by dotted lines. Owing to thisalternation of the layers the joints between the end edges 8 and 9 andthose between the longitudinal edges 10 and 11 of the differentlaminations 6 and 7 of any layer are overlapped by laminations 7 and 6of adjacent layers. If, moreover, the laminations 6 and 7 are made solong, that their end edges 12, 13 at the free ends of the yoke arms liein offset relation, also the joints lying in any layer between thelaminations of the yoke arms 2 and those of the coupling members 4 willbe overlapped by laminations of adjacent layers, so that a goodmechanical connection between the yoke arms and the coupling members ispossible.

In the embodiment illustrated in FIGS. 1 and 2 the end edges 8 and 9 ofthe laminations 6 and 7 do not have the same lengths. This is caused inthat the angles enclosed by said end edges 8 and 9 and said longitudinaledges 10 and 11 of those laminations 6 and 7 are both 60, that meansequal, whereas said laminations 6 and 7 have unequal widths. The resultthereof is that in the magnetic core structure there are cavitiesbetween the layers, which locally force the magnetic field from a layerinto the adjacent layers. These cavities have been avoided in theconstruction of the yoke members shown in FIG. 3. Therein each yoke armconsists of a narrower lamination 14 having end edges 15 and 16 andlongitudinal edges 17 and 18 and a broader lamination 19 having endedges 20 and 21 and longitudinal edges 22 and 23. The angle enclosed bythe end edge 15 and the longitudinal edge 17 of the lamination 14 is somuch smaller than 60 and the angle enclosed by the end edge 20 and thelongitudinal edge 22 of the lamination 19 is so much greater than 60, asto form together an angle of 120 and to make the end edges 15 and 20 ofequal lengths. In that case also the longitudinal edges 17 and 22 andthe longitudinal edges 18 and 23 of laminations of different yoke armsabutting each other with their end edges 15 and 20 meet, so that thecavities are suppressed and in each layer the transition from alamination of any given yoke arm to a lamination of another yoke arm isas favorable as possible.

It is observed, that not all layers of the yoke members need beconstructed in the manner suggested in accordance with the invention.Such layers may be locally alternated in the core structure by layers,which are quite differently constructed.

What I claim is:

1. A laminated magnetic core structure for a transformer or a choke coilof great power, comprising three leg members extending with theircentral longitudinal axes in the longitudinal edges of an equilateralprism, two star-shaped yoke members, each of which consists of threeabutting yoke arms enclosing angles of and having central longitudinalaxes, which intersect in a common point, and coupling members, each ofwhich connects an end of a leg member with the free end of a yoke arm,and in which core structure in at least a part of the total number oflayers of laminations of the yoke members each yoke arm abuts the twoother yoke arms with two straight end edges enclosing an angle of 120,the projections of said end edges on a line extending in the directionof the width of the yoke arm having unequal lengths, characterized inthat in the said layers each yoke arm consists of two laminationsextending side by side and abutting each other with longitudinal edgeswhich are parallel to the central longitudinal axis of the relevant yokearm, each one of said laminations being bounded at its end facinganother yoke arm by a straight end edge only, so that said laminationshave widths which are equal to the said projections of said end edges,and the angular points defined by said end edges and the abuttinglongitudinal edges of the said two laminations of each yoke arm lying inoffset relation to each other in the direction of said longitudinaledges.

2. A laminated magnetic core structure according to claim 1,characterized in that in the said layers of the yoke members each yokearm consists of two laminations, of which the end edges abutting the twoother yoke arms have the same lengths.

References Cited UNITED STATES PATENTS 2,367,927 1/ 1945 Chubb 336219 XR2,456,459 12/ 1948 Somerville 336-217 XR 2,594,001 4/1952 Ellis et a1336-210 X R 3,195,090 7/1965 Burkhardt et al. 3362l7 XR LEWIS H. MYERS,Primary Examiner.

T. J. KOZMA, Assistant Examiner.

US. Cl. X.R. 336-217

